Encapsulating Metallic Lithium into Carbon Nanocages Which Enables a Low-Volume Effect and a Dendrite-Free Lithium Metal Anode

Ferrocene-Based Artificial Interfacial Layer for High-Performance Lithium Metal Anodes: Continuous Regulation of Li+ Diffusion Behavior

The diversified design of hybrid artificial layers is a promising method for suppressing the Li dendrite growth and maintaining high Colombic efficiency of lithium (Li) metal anode. Previously, various kinds of organic/inorganic hybrid artificial layers were constructed on the Li metal anode and possessed a positive effect on electrochemical performance. However, the tunable synthesis of artificial layers to continuously regulate the Li diffusion behavior remains a challenge. In this work, the Li diffusion behavior could be tuned by modulating the proportion of components (LiClO₄, PMMA and ferrocene (Fc)) in the hybrid artificial layer (LF layer). After optimizing the proportion of each component, the resultant artificial SEI layer exhibits a high Li⁺ transference number (t_Li+ = 0.66) and a high Young's modulus (4.8 GPa). Based on the excellent properties of the as-constructed Fc-based artificial SEI layer, a high-performance lithium anode with no volume effect and dendrite growth is achieved. The Li||Li symmetric cells with a Fc-based artificial SEI layer yielded a stable cycle performance for 1500 h with a high current density of 10 mA cm^-2. The pouch cell with LF@Li anode coupled with high-loading LiFePO₄ cathode (12.8 mg cm^-2) exhibits excellent cyclic stability for 250 cycles with a capacity retention of 75% at 0.5C rate.

Advanced Current Collector Materials for High-Performance Lithium Metal Anodes

Lithium metal, as the "Holy Grail" of lithium battery anodes, is promising to be used in the next-generation of high-energy-density storage devices. However, serious safety risk and poor cycle performance are inevitable when bare lithium foil is used as the anode material, due to the uncontrolled growth of lithium dendrites, unstable solid electrolyte interface, and infinite volume expansion of lithium during cycling, which largely hinder the further commercial application of lithium metal batteries (LMBs). The utilization of up-to-date current collectors with specific composition and structure is believed to be effective to overcome these shortcomings. However, a systematic evaluation of the merit of different current collector materials for realizing high-performance lithium metal anodes is still lacking. This review summarizes the fashionable advanced current collector materials for long-life LMBs in recent years. The superiorities and related electrochemical performances by using these current collector materials are discussed in detail. It is expected that this review may promote the rational choice of appreciatory current collector materials with unique structure designs to extend the cycle life of lithium metal anodes for achieving the next-generation of high-energy-density LMBs.

Lithium/Graphene Composite Anode with 3D Structural LiF Protection Layer for High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs) are a promising candidate for next-generation energy storage devices. However, the high irreversibility and dead Li accumulation of the lithium metal anode caused by its fragile original solid electrolyte interface (SEI) seriously hinder the practical application of LMBs. Herein, a facile slurry-coating and one-step thermal fluorination reaction method is proposed to construct the 3D structural LiF-protected Li/G composite anode. The existence of a 3D LiF protection layer is convincingly confirmed and the function of the Li/G skeleton is discussed in detail. The 3D structural LiF protection layer results in superior electrochemical performance by improving the utilization of Li and suppressing the accumulation of dead Li in symmetric and full coin cells. Moreover, a 0.85 Ah pouch cell strictly following the parameters of the practical battery industry can work stably for 140 cycles with a gradual internal resistance increase. This novel Li/G composite anode indicates a promising strategy in lithium/carbon composite anodes for LMBs, and the facile thermal fluorination reaction method presented in this paper offers a new method for the construction of a 3D structural protection layer for lithium metal anodes.

Self-Assembly Lightweight Honeycomb-Like Prussian Blue Analogue on Cu Foam for Lithium Metal Anode

As a next-generation anode material for lithium batteries, Li metal anode suffers from inherent drawbacks such as infinite volume expansion and uneven Li plating/stripping. Herein, we propose a lightweight lithiophilic Prussian blue analogue (PBA) with honeycomb-like structure on Cu foam by self-assembly method to address these issues. The unique honeycomb-like architecture could provide enlarged surface areas and abundant deposition sites for homogenizing Li⁺ flux during Li plating. Consequently, the elaborate PBA-decorated Cu foam current collector enables long-term (1800 h) reversible plating/stripping behavior and an observably improved Coulombic efficiency (98.3% after 350 cycles). The concept of the direct self-assembly synthesis method on metal foam provides new insights into the design of a lightweight 3-dimensional current collector for Li metal anode.

Flexible MnO nanoparticle-anchored N-doped porous carbon nanofiber interlayers for superior performance lithium metal anodes

The mounting requirements for electric apparatus and vehicles stimulate the rapid progress of energy storage systems. Lithium (Li) metal is regarded as one of the most prospective anodes for high-performance cells. However, the uneven dendrite growth is one of the primary conundrums that hampers the use of the Li metal anode in rechargeable Li batteries. Achieving even Li deposition is crucial to solve this concern. In this study, a stable interlayer based on electrospun flexible MnO nanoparticle/nitrogen (N)-doped (polyimide) PI-based porous carbon nanofiber (MnO-PCNF) films was effectively prepared via electrospinning and in situ growth of MnO to reduce the growth of Li dendrites. It is revealed that the attraction of implanted MnO towards Li, the lithiophilic nature of N dopants and the capillary force of porous architectures are beneficial to the preeminent Li wettability of the MnO-PCNF interlayer. Furthermore, the wettable, stable and conductive structure of the MnO-PCNF interlayer can be retained well, offering rapid charge transfer to Li redox reactions, reduced local current density during the cycling process and homogeneous distribution of deposited Li. Consequently, anodes with MnO-PCNF interlayers can relieve the volume change and inhibit the growth of Li dendrites, demonstrating a remarkable lifetime for lithium metal cells at high current.

A 3D-mixed ion/electron conducting scaffold prepared by in situ conversion for long-life lithium metal anodes

Lithium (Li) metal is widely considered the most promising anode material because of its ultrahigh specific energy. However, the obvious volume change and uncontrollable dendrite growth hinder its commercial applications. Herein, we designed a 3D scaffold of Cu₃P nanoarray-modified Cu foam via in situ conversion (3D MIECS). Uniform lithiophilic Cu₃P nanoarrays were in situ grown inside the Cu foam (Cu₃P NA@CF) that presented a high specific surface area and very low nucleation overpotential. Specifically, the lithiated Cu₃P nanoarrays possess the features of mixed ion/electron conductivity and structural stability responsible for uniform Li deposition in the whole three-dimensional space of the metal skeleton, showing scarcely any volume expansion or structural collapse during the continuous Li plating/stripping process. Therefore, the modified Cu foam host achieves dendrite-free cycling over 600 cycles at a current density of 3 mA cm^-2 with a coulombic efficiency (CE) of 99.1%. A 3D MIECS-Li||LiFePO₄ full cell holds a capacity retention of 80% with a stable CE of 99.63% over 1000 cycles at 3 C.

Advances in the Design of 3D-Structured Electrode Materials for Lithium-Metal Anodes

Although the lithium-metal anode (LMA) can deliver a high theoretical capacity of ≈3860 mAh g^-1 at a low redox potential of -3.040 V (vs the standard hydrogen electrode), its application in rechargeable batteries is hindered by the poor Coulombic efficiency and safety issues caused by dendritic metal growth. Consequently, careful electrode design, electrolyte engineering, solid-electrolyte interface control, protective layer introduction, and other strategies are suggested as possible solutions. In particular, one should note the great potential of 3D-structured electrode materials, which feature high active specific surface areas and stereoscopic structures with multitudinous lithiophilic sites and can therefore facilitate rapid Li-ion flux and metal nucleation as well as mitigate Li dendrite formation through the kinetic control of metal deposition even at high local current densities. This progress report reviews the design of 3D-structured electrode materials for LMA according to their categories, namely 1) metal-based materials, 2) carbon-based materials, and 3) their hybrids, and allows the results obtained under different experimental conditions to be seen at a single glance, thus being helpful for researchers working in related fields.

A Three-Dimensional Nano-web Scaffold of Ferroelectric Beta-PVDF Fibers for Lithium Metal Plating and Stripping

Lithium metal has been considered as an anode material to improve energy densities of lithium chemistry-based rechargeable batteries (that is to say, lithium metal batteries or LMBs). Higher capacities and cell voltages are ensured by replacing practically used anode materials such as graphite with lithium metal. However, lithium metal as the LMB anode material has been challenged by its dendritic growth, electrolyte decomposition on its fresh surface, and its serious volumetric change. To address the problems of lithium metal anodes, herein, we guided and facilitated lithium ion transport along a spontaneously polarized and highly dielectric material. A three-dimensional web of nanodiameter fibers of ferroelectric beta-phase polyvinylidene fluoride (beta-PVDF) was loaded on a copper foil by electrospinning (PVDF#Cu). The electric field applied between the nozzle and target copper foil forced the dipoles of PVDF to be oriented centro-asymmetrically and then the beta structure induced ferroelectric polarization. Three-fold benefits of the ferroelectric nano-web architecture guaranteed the plating/stripping reversibility especially at high rates: (1) three-dimensional scaffold to accommodate the volume change of lithium metal during plating and stripping, (2) electrolyte channels between fibers to allow lithium ions to move, and (3) ferroelectrically polarized or negatively charged surface of beta-PVDF fibers to encourage lithium ion hopping along the surface. Resultantly, the beta-PVDF web architecture drove dense and integrated growth of lithium metal within its structure. The kinetic benefit expected from the ferroelectric lithium ion transport of beta-PVDF as well as the porous architecture of PVDF#Cu was realized in a cell of LFP as a cathode and lithium-plated PVDF#Cu as an anode. Excellent plating/stripping reversibility along repeated cycles was successfully demonstrated in the cell even at a high current such as 2.3 mA cm^-2, which was not obtained by the nonferroelectric polymer layer.

Inducing the Formation of In Situ Li3N-Rich SEI via Nanocomposite Plating of Mg3N2 with Lithium Enables High-Performance 3D Lithium-Metal Batteries

Lithium metals fit the growing demand of high-energy density rechargeable batteries because of their high specific capacity and low redox potential. However, the lithium-metal anodes are abandoned because of various defects. In this study, we apply composite plating into the protection of lithium-metal anodes. We confirmed that the Mg₃N₂ nanoparticle dispersed in the ether electrolyte can be easily composite-plated with lithium, resulting in a flat, dense, and dendrite-free lithium deposition layer during the electrodeposition process. In addition, the Mg₃N₂ plated in the lithium metal phase would react with lithium and then generate a Li₃N-rich solid electrolyte interphase (SEI) layer, mitigating continuous side reactions of the electrolyte on the Li metal. In addition, another product of the reaction is Mg which can work as lithiophilic sites in electrodeposition. The combined effect of the two fields can effectively improve the performance of lithium metal anodes. The Li₃N-rich SEI layer would grow well on the surface of the three-dimensional (3D) lithium anode by composite plating. Furthermore, composite plating with the Mg₃N₂-containing electrolyte is a viable route that can be used for various 3D current collectors easily with a small volume effect. Here, we show that the composite plating 3D lithium metal anode is successfully applied in the Li-S battery with a long lifetime.